The present disclosure relates to the subject matter contained in Japanese Patent Application No. 2001-49544 filed on Feb. 26, 2001 and Japanese Patent Application No. 2002-39545 filed on Feb. 18, 2002, which are incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a motion picture code evaluation apparatus and in particular to a motion picture code communications evaluation technology to evaluate a code and a protocol used for transmission/reception of digital motion picture data.
2. Description of the Related Art
The digital motion picture is a temporal link of instantaneous pictures called motion frames (hereinafter referred to as frames). The digital motion picture generally has enormous data amount. Therefore, generally, compression of information, that is, encoding is made to perform data transmission/reception and the received data is decoded to play back the motion picture.
For example, international standards of the motion picture codes include MPEG (Moving Picture Experts Group)xe2x80x942 (ISO/IEC13818) and MPEG-4 (ISO/IEC14496) by the ISO/IEC (International Organization for Standardization/International Electrotechnical Commission) and H.261 and H.263 by the ITU (International Telecommunication Union) recommendations.
The aforementioned motion picture code comprises pixels arranged in a shape of a lattice. For example, the CIF format comprising 352 horizontal pixels by 288 vertical pixels and the QCIF format comprising 176 horizontal pixels and 144 vertical pixels are used.
The number of pixels composing a frame is also called the screen size.
In the case of a color picture, for example, in the CIF, the number of pixels includes a luminance screen (Y information) and two chrominance screens (U and V information) There are, for example, 4:2:0 format where one pixel is assigned to the U information of the chrominace screens and one pixel is assigned to the V information of the chrominance screens per the luminance screen having 2 by 2 pixels, 4:2:2 format where one pixel is assigned to the U information the chrominance screens and one pixel is assigned to the V information the chrominance screens per the luminance screen having 2 pixels, and the like.
The 4:2:2 format has twice the number of the pixels in the chrominance screens as many as the 4:2:0 format.
In some case, three primary colors such as RGB (red, green, blue) may be used to represent each of pixels.
In the case of color image, the number of pixels refers to all pixels of the luminance and the chrominance or the three primary colors.
It goes without saying that the more the number of pixels per frame are, the more minute, that is, the higher quality picture is obtained.
The number of frames per unit time is, for example, 30 frames per second or 15 frames per second. The greater this value is, the smoother action is represented, that is, the higher quality picture is obtained.
In digitally representing the brightness, the intermediate gradation levels are quantized from the darkest black to the brightest white.
In such a case, the number of the quantization levels are finite and around 256 levels of gray gradation that can be visually represented in eight bits are used in general applications.
Or, the number of colors represented digitally is finite and around 16 million colors are used.
The number of colors may be referred to as the number of quantization levels.
Unless there is particular reason, the number of quantization levels is the number of colors in the case of color image.
Also, the number of gray quantization levels is greater, the higher quality picture is obtained.
The value obtained by totaling the gray quantization levels in a specific time over all the pixels in the frames is called a motion picture information amount.
Generally, the number of pixels and the number of frames per second are constant but may change the number of pixels or frames.
The number of quantization levels may vary within a frame.
For load applied on a transmission path, a transmitter and a receiver, the smaller amount of motion code provides smaller load.
Thus, an amount of motion picture codes in relation to an amount of an image before information compression, that is, the higher compression ratio or the more coding efficiency is desirable.
For motion codes specified in the international standards or equivalent, the realized encoding efficiency is limited. In order to reduce the load on a transmission path, a transmitter and a receiver, it is practically efficient to reduce the number of pixels, frames and gray quantization levels actually. However, this degrades the picture quality.
An actual operation for compensating the load on a transmission path, a transmitter and a receiver in the transmission of motion pictures requires high cost so that services may be operated by setting the higher charge for the larger amount of motion picture information.
Quality degradation of motion pictures caused by transmission of a motion picture code will be described.
In transmission/reception of a motion picture code, a motion picture received at a receiving party suffers from degradation compared with an original motion picture due to the following causes:
Firstly, a motion picture code is not correctly received due to a transmission error.
Secondly, transmission in packets results in loss of some of the packets halfway and the lost packets are not received.
Thirdly, transmission/reception of a motion picture code takes too much time and displaying after decoding of a motion picture frame is delayed from the timing of regeneration of motion picture, which already have started, so that the display of the motion picture frame is skipped and execution proceeds to processing of the next motion picture frame.
A part of an original motion picture, which is failed to be decoded and be displayed, is referred to a motion picture loss.
Depending on which part of the motion picture code the error occurred in, the transmission error has different influences on the motion picture to be decoded and to be displayed.
A parameter representing specifications of the entire motion picture code such as the screen size, and the chrominance format of a motion picture code or a part of the motion picture code that accommodates codes related to the predictive encoding system for the entire frame and prediction method is referred to a header.
In case that a transmission error has occurred in the header section, decoded display of the entire motion picture is disabled or decoded display of the entire frame is disabled.
In case that a transmission error has occurred in the section related to the gradation of pixels in a frame, decoded display of only corresponding pixels may be disabled.
In this way, there are not a specific relationship between the amount of motion picture code not used for decoded display due to a transmission error or delay and the amount of motion picture loss in a motion picture after decoding. Thus it is necessary to evaluate the motion picture loss in each time.
Assume that a motion picture code is transmitted in the CIF format at present and a service is performed to change to the transmission of a motion picture in QCIF format in accordance with congestion of a transmission path and worsening of transmission error ratio. In this case, the quality of a motion picture is roughly classified into two stages.
The CIF and QCIF formats have 352 horizontal pixels by 288 vertical pixels and 176 horizontal pixels by 144 vertical pixels, respectively. Therefore, difference in the amount of motion picture information between the CIF and QCIF formats is four times.
When several percents of motion picture loss is caused due to the transmission error, the difference in the amount of motion picture information between the CIF and QCIF formats is in a range of 3.8 to 4.2 times.
Even if charging is made in proportion to an amount of correctly transmitted motion picture information, the number of pixels and the number of frames (in other words, which format the motion picture is transmitted in) greatly influence on the amount of correctly transmitted motion picture information and the several percents of motion picture loss has one tenth as influence on the amount of correctly transmitted motion picture information as the difference between the formats as described above.
A motion picture code evaluation apparatus according to the related art decodes a received motion picture code to determine the motion picture loss. Therefore, even if one frame has fifty thousand pixels, the apparatus calculates the amount of motion picture loss in accuracy of 0.0002 percent.
However, as mentioned earlier, since the motion picture loss does not greatly influence on the amount of the motion picture information, it is sufficient to obtain the amount of the motion picture loss in an accuracy of several percents. Therefore, the processing scale to decode all the pixels to determine the motion picture loss is an excessive load on the receiver.
In a situation where progress in transmission technologies are eminent, transmission capacity is ever-increasing and motion picture code rate is getting higher, it is quite important to reduce the processing load especially on the receiver.
An object of the invention is to provide a motion picture code evaluation apparatus which detects that whether frame header of motion picture code is abnormal or not and extracts motion picture coding parameter included in the frame header, and thereby being able to evaluate the motion picture loss without decoding the motion picture code and can reduce the processing load.
According to a first aspect of the invention, there is provided a motion picture code evaluation apparatus for evaluating an amount of motion picture information after transmission, the apparatus comprising:
a header inspection unit for inspecting a frame header and determining that whether the frame header is abnormal or not to calculate frame loss ratio every predetermined time;
an extracting unit for extracting motion picture coding parameter from the frame header and detecting variation of the motion picture coding parameter in the predetermined time; and
an amount-of-motion-picture-information calculating unit for summing the motion picture coding parameter and weight, which is based on the variation of the motion picture coding parameter, to calculate an ideal amount of motion picture information every predetermined time,
wherein an actual amount of motion picture information is calculated by multiplying the ideal amount of motion picture information by (1xe2x88x92the frame loss ratio).
According to a second aspect of the invention, there is provided the apparatus according to the first aspect of the invention,
wherein the motion picture coding parameter includes number of pixels of motion picture, frame rate, and number of quantization levels; and
wherein the extracting unit detects a ratio of frames in which each of the number of pixels, the frame rate, and the number of quantization levels continues to have the same value to the predetermined time.
According to a third aspect of the invention, there is provided the apparatus according to the second aspect of the invention,
wherein the number of pixels, the frame rate, and the number of quantization levels, which are included in the frame header determined abnormal, are ignored; and
wherein the number of pixels, the frame rate, and the number of quantization levels, which are included in the frame header just before the abnormal frame header, are assumed to continue.
According to a fourth aspect of the invention, there is provided the apparatus according to any one of the second and third aspects of the invention,
wherein the number of quantization levels is extracted while the number of quantization levels included in a header belonging to a lower layer than the frame is taken into consideration in addition to the number of quantization levels included in the frame header.
According to a fifth aspect of the invention, there is provided the apparatus according to any one of first to fourth aspects of the invention, wherein the extracting unit has one of timer and counter, which is reset when the extracting unit extracts the parameter different from the parameter included in the immediately preceding frame header.
According to a sixth aspect of the invention, there is provided a motion picture transmission network system comprising:
a motion picture code evaluation apparatus for evaluating an amount of motion picture information after transmission, the apparatus comprising:
a header inspection unit for inspecting a header and determining that whether the frame header is abnormal or not to calculate frame loss ratio every predetermined time;
an extracting unit for extracting motion picture coding parameter from the frame header and detecting variation of the motion picture coding parameter in the predetermined time; and
an amount-of-motion-picture-information calculating unit for summing the motion picture coding parameter and weight based on the variation of the motion picture coding parameter to calculate an ideal amount of motion picture information every predetermined time; and
a network management apparatus for managing transmission of the motion picture code;
wherein an actual amount of motion picture information is calculated by multiplying the ideal amount of motion picture information by (1xe2x88x92the frame loss ratio);
wherein the motion picture code evaluation apparatus outputs the frame loss ration to the network management apparatus; and
wherein at least one of screen size of the motion picture code, and the chrominance format of the motion picture code, the frame rate, the number of quantization levels is changeable in a transmission source of the motion picture code.
According to a seventh aspect of the invention, there is provided an accounting system comprising:
a motion picture code evaluation apparatus for evaluating an amount of motion picture information after transmission, the apparatus comprising:
a header inspection unit for inspecting a header and determining that whether the frame header is abnormal or not to calculate frame loss ratio every predetermined time;
an extracting unit for extracting motion picture coding parameter from the frame header and detecting variation of the motion picture coding parameter in the predetermined time; and
an amount-of-motion-picture-information calculating unit for summing the motion picture coding parameter and weight based on the variation of the motion picture coding parameter to calculate an ideal amount of motion picture information every predetermined time; and
an accounting apparatus for charging for motion picture transmission service
wherein an actual amount of motion picture information is calculated by multiplying the ideal amount of motion picture information by (1xe2x88x92the frame loss ratio);
wherein the motion picture code evaluation apparatus outputs the actual amount of motion picture information to the accounting apparatus; and
wherein the accounting apparatus charges based on quality of received motion picture.